1. Field of the Invention
The present invention relates to an in-mold foam molding equipment (hereinafter called in-mold molding equipment) for manufacturing one molded article, or a molded article having two or more molded portions different in characteristics, and more particularly to an in-mold molding equipment capable of suppressing occurrence of holes and defects as cause of drop of strength and also suppressing occurrence of large protrusions in the boundary of molded portions having different characteristics in one molded article or its periphery, and an in-mold molding method using such equipment.
2. Description of the Related Art
Hitherto, as a method of increasing the strength and reducing the weight partially in a molded article, it has been attempted to divide one molded article into plural portions, and the individual pieces are molded, and then integrated into one molded article. In this method, using two or more pair of metal molds corresponding to the shape of each portion, each metal molding space is filled with foamed beads corresponding to the required characteristics of each portion, and partial molded articles are formed. The individual molded articles are mutually adhered, and one molded article is formed. In this method, metal molds must be manufactured for individual portions, and as the number of divisions increases, the entire manufacturing process is complicated and the efficiency is extremely poor.
By contrast, an in-mold molding equipment is proposed, in which a pair of metal molds is divided into plural molding spaces by using a partition member, and each space is filled with different foamed beads, without being mixed, and an article is integrally molded in a pair of metal molds. In this in-mold molding equipment, the partition member is provided in a molding space by way of an actuator such as air cylinder through a cavity mold or a core mold, and this partition member divides the molding space into plural molding spaces. Each space is connected to at least one filling device for supplying individual foamed beads. That is, in the molding spaces divided by the partition member, plural foamed beads different in characteristics are supplied into individual spaces. After filling with beads, the partition member is drawn back. In the midst of withdrawing or after withdrawing, steam is supplied into mutually adjacent molding spaces, and foamed beads are heated and melted, and a molded article is obtained (for example, see patent document 1).
Moreover, in-mold foam molding equipment is proposed, in which a partition member of comb tooth structure arranged in narrow intervals not allowing to pass foamed beads is fixed and disposed at least to one of cavity mold or core mold to divide the molding space into plural sections, and foamed beads are supplied into divided spaces, and heated and melted, so that an integrated foamed molded article is manufactured (for example, see patent document 2).
In addition, in-mold foam molding equipment is proposed, in which a partition member having comb tooth structure with narrow intervals not allowing to pass foamed beads to be filled is disposed in a molding space, at the leading end of a movable partition board for dividing the molding space into plural molding spaces (for example, see patent document 3).
[Patent Document 1]
    JP 1999-334501 Unexamined Patent Publication (Kokai)[Patent Document 2]    JP 2001-150471 Unexamined Patent Publication (Kokai)[Patent Document 3]    JP 2002-172642 Unexamined Patent Publication (Kokai)
According to these methods, suppressing the number of molding processes for molded article, foamed beads can be changed depending on the positions of the molded article, and an integral molded article different in mechanical properties and visual features depending on the position of the molded article can be manufactured. Therefore, such methods are effective to enhance the quality and properties of molded article easily and outstandingly, and are widely employed in core materials for automobile bumpers, or cushion materials for packaging household electric products and furniture.
In the method by the molding equipment disclosed in patent document 1, since the partition member is a plate structure, depending on the shape of the cavity mold, large protrusions are consequently formed by molding after drawing back the partition member inserted in the molding space through the core mold, and it is attempted to suppress occurrence of large protrusions by using a pair of metal molds having the inner peripheral walls of the cavity mold positioned above and below the partition member projecting into the molding space. However, in the obtained molded article, large groove defects are formed around the location of the partition member when filling with foamed beads, and the strength of the molded article is lowered.
In the method by the molding equipment disclosed in patent document 2, since the partition member is lying across the molding space in the expanding and molding process, deep holes corresponding to the comb tooth partition member are formed in the molded article, and the strength of the molded article is lowered. In the method by the molding equipment disclosed in patent document 3, the comb tooth member is installed in the molding space in the molding process, as a result, multiple deep holes corresponding to the comb tooth member are formed in the molded article at positions corresponding to the location of the comb tooth member.
When the molded article is manufactured for the purpose of energy absorbing material, such defects and holes are serious problems. The energy absorbing material is supposed to absorb the impact when a strong impact is applied from outside. In the molded article having peripheral defects or multiple deep holes, when impact is applied, destruction of molded article is likely to occur with a central focus on these peripheral defects and multiple deep holes, and the strength is lowered as compared with the molded articles free from such peripheral defects or multiple deep holes. In particular, in a small molded article or thin molded article, effects of such strength reduction are significant.